Revert "Give internal classes hidden visibility."

It works with clang, but GCC has different rules so we can't make all of those
hidden. This reverts commit r190534.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190536 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/InterferenceCache.h b/lib/CodeGen/InterferenceCache.h
index a7fb980..c02fb9a 100644
--- a/lib/CodeGen/InterferenceCache.h
+++ b/lib/CodeGen/InterferenceCache.h
@@ -21,7 +21,7 @@
 
 class LiveIntervals;
 
-class LLVM_LIBRARY_VISIBILITY InterferenceCache {
+class InterferenceCache {
   const TargetRegisterInfo *TRI;
   LiveIntervalUnion *LIUArray;
   MachineFunction *MF;